Imagine not attacking the food supply of your enemy, because then your enemy would then attack your food supplies, and you would both go to bed hungry. Imagine trying to keep secret that you let them eat so that you can eat.
Imagine the guy sleeping beside you, uninjured, getting bit in the face by a rat, and dying from the diseases in the bite. Imagine trying to defend your friends from the rats.
Imagine suffocating because of poison gas, because your gas mask got fucked up from shell shrapnel. Imagine passing out from poison gas, and waking up at home, thousands of miles away from your friends, with a disability pension and a general hope you would be able to see again.